CN102686418B - Tracking filter apparatus for wheel monitoring systems - Google Patents

Tracking filter apparatus for wheel monitoring systems Download PDF

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Publication number
CN102686418B
CN102686418B CN201080052199.2A CN201080052199A CN102686418B CN 102686418 B CN102686418 B CN 102686418B CN 201080052199 A CN201080052199 A CN 201080052199A CN 102686418 B CN102686418 B CN 102686418B
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signal
filter
wheel
filtering
frequency
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CN102686418A (en
Inventor
C.安斯沃思
S.斯特拉恩
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Schrader Electronics Ltd
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Schrader Electronics Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
    • B60C23/02—Signalling devices actuated by tyre pressure
    • B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
    • B60C23/02—Signalling devices actuated by tyre pressure
    • B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
    • B60C23/0408—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H11/00—Networks using active elements
    • H03H11/02—Multiple-port networks
    • H03H11/04—Frequency selective two-port networks
    • H03H11/12—Frequency selective two-port networks using amplifiers with feedback
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H11/00—Networks using active elements
    • H03H11/02—Multiple-port networks
    • H03H11/04—Frequency selective two-port networks
    • H03H11/12—Frequency selective two-port networks using amplifiers with feedback
    • H03H11/1291—Current or voltage controlled filters
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H2210/00—Indexing scheme relating to details of tunable filters
    • H03H2210/02—Variable filter component
    • H03H2210/021—Amplifier, e.g. transconductance amplifier
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H2210/00—Indexing scheme relating to details of tunable filters
    • H03H2210/04—Filter calibration method
    • H03H2210/043—Filter calibration method by measuring time constant

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Measuring Fluid Pressure (AREA)
  • Surgical Instruments (AREA)
  • Filters That Use Time-Delay Elements (AREA)
  • Networks Using Active Elements (AREA)

Abstract

A wheel monitoring system that includes a tracking filter apparatus for tracking a signal that has a varying main frequency. The tracking filter apparatus has an adjustable filter and a filter controller arranged to measure the amplitude of the filtered signal and to compare amplitude against a reference value. The filter controller adjusts the cut off frequency of the filter if the measured amplitude differs from the reference value by an amount that exceeds a threshold value. The filter controller adjusts the cut off frequency such that the main frequency lies within the roll off region of the filter's frequency response. The system may be used to track signals that are produced by shock sensors in a wheel mounted monitoring device.

Description

For the tracking filter apparatus of wheel supervisory system
Technical field
The present invention relates to the filter for following the tracks of electric signal, described electric signal is in particular the signal sent from the swivel wheel of the wheel of such as moving vehicle.Particularly, the present invention relates to the filter of the monitoring equipment for being installed on wheel.
Background technology
The electric signal sent from the device wheel of vehicle generally includes a considerable amount of signal noise, particularly when vehicle is advanced on rough earth.In some cases, expect that the component of signal detected depends on wheel velocity, this makes from noise, extract desired signal components complexity.
Such as, US Patent 7,367,227 disclose a kind of tire pressure monitoring system (TPMS), wherein comprise a pair shock sensor at the tire pressure measuring equipment being installed on wheel, shock sensor produces electric signal, can infer the position of corresponding wheel on vehicle from this electric signal.The electric signal produced by shock sensor comprises master signal component and signal noise, and described master signal component represents the output of shock sensor.The frequency of signal noise and amplitude, fully close to frequency and the amplitude of master signal component, make may be difficult to reliably detect master signal component.In addition, the frequency of master signal component is determined by the rotative speed of wheel.Frequency due to master signal component is unknown at first and it is variable, so which increase the difficulty detecting master signal component.As a result, conventional static filter reliably can not extract master signal component, particularly when vehicle is advanced on rough earth.When using other sensors of such as MEMS (MEMS) sensor or accelerometer, there is Similar Problems.
Thus, expect to provide a kind of filter that reliably can detect the electric signal sent from the device swivel wheel.
Summary of the invention
A first aspect of the present invention provides a kind of wheel supervisory system, comprise wheel monitoring equipment, described wheel monitoring equipment can be installed on described wheel, and be configured to the first signal of the feature generating the described wheel of instruction, described wheel in use has variable rotational speed, described first signal has the basic frequency depending on described variable rotational speed, and wherein said wheel supervisory system comprises tracking filter apparatus further, and described tracking filter apparatus comprises:
Input, for receiving described first signal;
Adjustable filter, be arranged to the first signal receiving described first signal and produce through filtering, described adjustable filter has adjustable cutoff frequency; And
Filter controller, be arranged at least one feature measuring described the first signal through filtering, and at least one feature measured described and reference value are compared, described filter controller and described adjustable filter co-operating, if the amount different from described reference value at least one feature measured described exceedes threshold value, then adjust described cutoff frequency.
Described threshold value can be zero, maybe can be set to the level allowing tolerance limit in the comparison.
The first signal through filtering typically has the master signal component at described basic frequency place, and described master signal component has amplitude, and described in described the first signal through filtering, at least one feature comprises described amplitude expediently.
In a preferred embodiment, adjustable filter has the frequency response comprising (roll off) district of roll-offing, in the described decay of the application of filter described in district with change of frequency of roll-offing, described filter controller is arranged to the cutoff frequency adjusting described filter, make described basic frequency be in described in roll-off in district.
In certain embodiments, tracking filter apparatus can to described the first signal application through filtering independent of the gain of frequency, described frequency controller can be arranged to the cutoff frequency adjusting described filter in this case, make described basic frequency be in described in the following position of roll-offing in district: in this position, the described decay of described filter application cancels the described gain independent of frequency at least in part on the impact of described the first signal through filtering.The decay that described filter can be applied at described cutoff frequency place than described filter in the described decay of described described location application of roll-offing in district is higher.
Alternatively, described filter cancels the described gain independent of frequency to the impact of described the first signal through filtering substantially in the described decay of described described location application of roll-offing in district.
In a preferred embodiment, described first signal and each in the first signal of filtering described have the master signal component at described basic frequency place, corresponding master signal component has corresponding amplitude, described tracking filter apparatus is included in the amplifier between described input and described adjustable filter further, described amplifier be arranged to when roll-off described in described basic frequency is in the selected position in district time, the amplitude of described first signal is adjusted to the level impelling the amplitude of described the first signal through filtering substantially to mate described reference value.
Described adjustable filter can comprise low-pass filter, in this case, described filter controller and described adjustable filter co-operating, if the amount little for reference value described at least one aspect ratio measured described exceedes first threshold, then increase described cutoff frequency, if and the amount that described at least one aspect ratio measured described, reference value is large exceedes Second Threshold, then reduce described cutoff frequency.
As an alternative, described adjustable filter can comprise high-pass filter, in this case, described filter controller and described adjustable filter co-operating, if the amount large for reference value described at least one aspect ratio measured described exceedes first threshold, then increase described cutoff frequency, and if the little amount of reference value described at least one aspect ratio measured described exceed Second Threshold, then reduce described cutoff frequency.
In certain embodiments, such as, when described wheel monitoring equipment comprises tire pressure monitoring device, described wheel monitoring equipment comprises the first motion sensor, and described first signal is generated by described first motion sensor.In an exemplary embodiment, described first motion sensor comprises shock sensor, accelerometer or MEMS (MEMS) sensor.
More specifically, carrying out tracking filter apparatus of the present invention can use together with the incoming signal produced from any equipment of particularly sensor, wherein needs the dominant frequency component extracting incoming signal from noise.
Thering is provided two sensors (or other equipment), each generation has the corresponding output signal of identical fundamental frequency component, and when wherein expecting the phase relation determined between two output signals, this tracking filter apparatus is particularly useful.
Such as, in certain embodiments, described wheel monitoring equipment comprises the second sensor (such as the second shock sensor or the second accelerometer or the second MEMS sensor), described second sensor generates the secondary signal of the described feature of the described wheel of instruction, described secondary signal has the basic frequency depending on described variable rotational speed, wherein said wheel supervisory system comprises the second tracking filter apparatus further, described second tracking filter apparatus comprises: input, for receiving described secondary signal, and adjustable filter, be arranged to the secondary signal receiving described secondary signal and produce through filtering, described adjustable filter has adjustable cutoff frequency, and wherein said filter controller is arranged at least one feature measuring the described secondary signal through filtering, and at least one feature measured described and described reference value are compared, the adjustable filter co-operating of described filter controller and described second tracking filter apparatus, if the amount different from described reference value at least one feature measured described exceedes threshold value, then adjust described cutoff frequency.
Described system may further include phase detectors, described first and second each in the signal of filtering are provided to described phase detectors, and described phase detectors are arranged to be determined in the described first and second phase relations between the signal of filtering.Under these circumstances, described wheel is typically installed on vehicle, and described system is arranged to and depends on that described phase relation carries out the determination about the position of described wheel on described vehicle.
Should or each tracking filter apparatus can be included in described wheel monitoring equipment, or can be separated with described wheel monitoring equipment and provide.
A second aspect of the present invention provides a kind of wheel monitoring equipment, described wheel monitoring equipment can be installed on described wheel, and be configured to the first signal of the feature generating the described wheel of instruction, described wheel in use has variable rotational speed, described first signal has the basic frequency depending on described variable rotational speed, wherein said wheel monitoring equipment comprises tracking filter apparatus further, and described tracking filter apparatus comprises: input, for receiving described first signal; Adjustable filter, be arranged to the first signal receiving described first signal and produce through filtering, described adjustable filter has adjustable cutoff frequency; And filter controller, be arranged at least one feature measuring described the first signal through filtering, and at least one feature measured described and reference value are compared, described filter controller and described adjustable filter co-operating, if the amount different from described reference value at least one feature measured described exceedes threshold value, then adjust described cutoff frequency.
A third aspect of the present invention provides a kind of method of dominant frequency component of the first signal followed the tracks of in wheel supervisory system, described wheel in use has variable rotational speed, described basic frequency depends on described variable rotational speed, wherein said wheel supervisory system comprises the adjustable filter with adjustable cutoff frequency further, and described method comprises: use described adjustable filter to carry out filtering to produce the first signal through filtering to described first signal; Measure at least one feature of described the first signal through filtering; At least one feature measured described and reference value are compared; And if at least one feature amount different from described reference value measured described exceedes threshold value, then adjust described cutoff frequency.
Expection the present invention can also be used for following the tracks of the signal except the signal except sending from swivel wheel.
Therefore, a fourth aspect of the present invention provides a kind of tracking filter apparatus, and described tracking filter apparatus comprises: input, for receiving the first signal, and the vicissitudinous basic frequency of described first signal tool; Adjustable filter, be arranged to the first signal receiving described first signal and produce through filtering, described adjustable filter has adjustable cutoff frequency; And filter controller, be arranged at least one feature measuring described the first signal through filtering, and at least one feature measured described and reference value are compared, described filter controller and described adjustable filter co-operating, if the amount different from described reference value at least one feature measured described exceedes threshold value, then adjust described cutoff frequency.
A fifth aspect of the present invention provides the method for the dominant frequency component of the first signal in a kind of track channel, this system comprises the adjustable filter with adjustable cutoff frequency, and described method comprises: use described adjustable filter to carry out filtering to produce the first signal through filtering to described first signal; Measure at least one feature of described the first signal through filtering; At least one feature measured described and reference value are compared; And if at least one feature amount different from described reference value measured described exceedes threshold value, then adjust described cutoff frequency.
Reading the following description of specific embodiment also with reference to after accompanying drawing, further advantage of the present invention will become obvious for those skilled in the art.
It must be most low-key (tone) in harmonic sequence that the term " basis " used in this frequency component about incoming signal is not intended to this frequency implicit.On the contrary, be intended to contain the frequency expecting any echo signal component followed the tracks of.Typically, but not necessarily, echo signal component is the dominant frequency component in incoming signal, and it can be or can not be the most low-key in harmonic sequence.
Accompanying drawing explanation
Now will by example embodiment of the invention will be described with reference to drawings, wherein:
Fig. 1 is the block diagram of the embodiment being combined the tire monitoring system (TMS) illustrated with the part of vehicle;
Fig. 2 is the block diagram of the tire monitor device that the TMS of Fig. 1 comprises;
Fig. 3 is the block diagram of the first tracking filter apparatus realizing one aspect of the present invention;
Fig. 4 is the figure of the frequency response representing low-pass filter;
Fig. 5 is the block diagram realizing a described aspect of the present invention and be shown as the second tracking filter apparatus of a part for the shock sensor interface cooperated with phase detection device; And
Fig. 6 A is the schematic diagram of the exemplary implementations that the second tracking filter apparatus is shown together with Fig. 6 B.
Detailed description of the invention
With reference now to Fig. 1 of accompanying drawing, show and be usually indicated as 102 the tire monitoring system (TMS) on vehicle 100 shown in original position.In order to clear, illustrate only those parts to understanding the helpful vehicle 100 of the present invention and TMS 102.
Vehicle 100 comprises wheel 104,106,108,110, and each wheel comprises the tire be arranged on wheel rim.TMS 102 comprises control unit 112(such as car engine control unit (ECU) or Body Control Module (BCM)) and tire monitoring device 124,126,128,130, be typically called as sensor, transmitter, wheel unit etc.Tire monitoring device 124,126,128,130 measures one or more tire characteristics (such as pressure and/or temperature), and sends corresponding tire data to be received by control unit 112 and to be processed.Typically, corresponding tire monitoring device is associated with each wheel of vehicle 100.
In an exemplary embodiment, tire monitoring device can be measured tire pressure and data are sent to control unit 112, comprises the data of the tire pressure measured by expression, and usually also comprises unique identification information identifying corresponding tire monitoring device.Each in tire monitoring device 124,126,128,130 comprises: the radio transmitters of suitably power supply is battery powered radio frequency (RF) transmitter expediently; And pressure sensor, for measuring the pressure of the gas (being generally air) in tire.In such embodiments, system 102 can be called tire pressure monitoring system (TPMS).
Any suitable control unit can be used in system 102.Such as, in the illustrated embodiment, control unit 112 comprises controller 132, storage equipment 134 and the receptor 136 for receiving transmission over radio from tire monitoring device.
With reference now to Fig. 2, show the block diagram of the embodiment of tire monitoring device 200.Tire monitoring device 200 comprise the power supply 204 of controller 202, such as battery, transmitter-responder 206, pressure sensor 208, one or more piezoelectric motion sensor 210,212, radio transmitters 214 and antenna 216.In this illustration, motion sensor 210,212 each comprise the corresponding shock sensor of the type producing electric signal in response to standing acceleration/accel (typically, shock sensor makes response to the change in acceleration/accel), the acceleration/accel of electric signal instruction experience, the change speed of the change typically be in acceleration/accel, particularly acceleration/accel, typically proportional with the change speed of the acceleration/accel experienced, the change typically be in acceleration/accel, particularly acceleration/accel.As an alternative, sensor 210,212 each can comprise accelerometer, accelerometer equipment or MEMS (MEMS) sensor.Essential difference between accelerometer and shock sensor is relevant to the change of the power being applied to shock sensor from the output signal of shock sensor, and proportional with the absolute force applied from the output signal of accelerometer.
During use, controller 202 can determine at least one aspect of the position of tire monitoring device based on the electric signal produced by shock sensor 210,212 along with rotation of wheel, such as its left side at vehicle or right side.
Shock sensor 210,212 can be used as motion switch or the rotation sensor of tire monitoring device 200.Shock sensor 210,212 can be combined to form twin-axis accelerometer, and determines the first acceleration/accel along the first axle and the second acceleration/accel along the second axle.Shock sensor 210,212 is examples for force snesor, displacement pickup or rotation sensor.Also shock sensor can be referred to as piezoelectricity rotation sensor.The force snesor of the piezoelectricity rotation sensor of other type or other types, displacement pickup, rotation sensor or motion sensor can be used to carry out alternative shock sensor described here.
Therefore, in the illustrated embodiment, both shock sensors 210,212 can be used as motion switch, to determine when tire moves and determine tire is positioned at which side of vehicle.Shock sensor 210,212 and controller 202 couple.
Any suitable method can be used to provide right/left from shock sensor 210,212 and/or cw/conter clockwise information.But, preferably, use the U.S. Patent No. 7 such as owned together by people such as Stewart, 367,227, title is for providing the system and method for right/left and/or cw/conter clockwise information disclosed in " Determination of Wheel Sensor Position UsingShock Sensors and a Wireless Solution ".Here, the first shock sensor 210 produces the first motor message, and the second shock sensor 212 produces the second motor message, and controller 202 is couple to the first shock sensor and the second shock sensor.Controller circuitry is configured to the right side-leftward position information determining about tire monitoring device based on the lag-lead relation of the first motor message and the second motor message.Such as, along with rotation of wheel, produce two waveforms by shock sensor, its phase 90 degree.Based on the direction of the rotation of wheel, i.e. cw or conter clockwise, axle is by leading or lag behind another axle.The acceleration/accel that they detect by shock sensor changes into the signal of such as voltage waveform.Then by the controller of tire monitoring device, these signals (comprising about the first signal of the acceleration/accel on an axle and the secondary signal about the acceleration/accel on the second axle) can be amplified, filtering and convert digital data to.Then the location information of the position about the tire comprising tire monitoring device can be determined based on this signal.Can carry out about tire monitoring device being rotating in a clockwise direction or the judgement rotated in a counter-clockwise direction based on the sampled signal from shock sensor subsequently.Location information can be determined, such as right-hand side location or left-hand side location from the direction rotated.Particularly, the controller of tire monitoring device can determine the first acceleration signal about x-axis and the second acceleration signal about z-axis delayed/the precondition.Controller determination x-axis is leading still lags behind z-axis signal.This delayed/leading information will instruction cw or left-hand revolution direction and the vehicle information of advancing forward instead of backward, and controller can determine that tire monitoring device is at the right-hand side of vehicle or left-hand side.Rotate for direction, disclosed method and apparatus can analyze+1g/-1g component alternately.
Can by suitable device, such as microprocessor, microcontroller or be programmed to other proper data treatment facilities performing function described here, realize controller 202.
In the illustrated embodiment, pressure sensor 208 detects the pneumatic air pressure of tire, and tire monitoring device 200 is associated with this pneumatic air pressure.In alternative embodiment, can supplement or alternative pressure sensor 208 with temperature sensor or other equipment for detecting tire data.The instruction of tire data is provided at input 220 place by controller 202.
Shock sensor interface 207 is provided in tire monitoring device 200, and is configured to provide necessary control signal, and detects the electric signal from shock sensor 210,212.Change in 210, the 212 pairs of acceleration/accels of shock sensor in one embodiment makes response, to produce with the output of charge signal output form.Output signal typically is the magnitude of 1mV/g.Shock sensor interface 207 receives electrical output signal, and it is simulation in essence, amplifies and filtering this signal, to provide corresponding treated output signal to controller 202.Shock sensor interface 207 operates in response to the control signal carrying out self-controller 202.Preferably, two shock sensors 210,212 can via multiplexing come shared same interface 207.
The output signal produced by each shock sensor comprises master signal component and with other component of signals of signal noise form.The frequency of noise component and amplitude, enough close to frequency and the component of master signal component, may be difficult to reliably detect master signal component thus.In addition, by the rotative speed of wheel, the rotative speed namely with wheel changes, and determines the frequency of master signal component.
Fig. 3 is the block diagram of the tracking filter apparatus 300 realizing one aspect of the present invention.Device 300 has input 301 for receiving incoming signal and for providing the output 302 of output signal.Incoming signal typically electricity, and depend on application can be analog or digital.Output signal is the treated version of incoming signal.It is filtering that the main process that will be performed by device 300 pairs of incoming signals operates, such as high pass, low pass or bandpass filtering, although can perform other process operations one or more as required.
The incoming signal that device 300 is particularly suitable for having variable frequency carries out filtering.Typically, incoming signal comprises more than one component of signal, and each component has its oneself corresponding frequencies, supposes at least one component of signal in this case, and---it can be called as main or basis signal component---has variable frequency.Under these circumstances, the function of tonic chord of device 300 can be by allowing master signal component to extract master signal component by other component of signals (it can be considered to noise) that decay simultaneously from incoming signal.Therefore, device 300 particularly but be not exclusively suitable for carrying out filtering to the electric signal sent from the equipment being installed on wheel.Device 300 can be merged into the equipment being installed on wheel, maybe can be still associated with it with the device separates being installed on wheel by device 300, to receive electric signal from it.By way of example, device 300 can be merged in tire monitoring equipment, or be associated with tire monitoring equipment.Under these circumstances, device 300 can receive by the electric signal of those shock sensors generation such as described above with reference to Fig. 1 and Fig. 2 as its incoming signal.Like this, device 300 is suitable for being merged in shock sensor interface 207, or in the similar assembly of suitable system.
Master signal component is the echo signal component that device 300 is expected to extract.Typically, but not necessarily, master signal component is led signal component and also can be called as fundamental frequency component.
In an exemplary embodiment, tracking filter apparatus 300 comprises signal pre-processing module 304, for performing one or more signal processing operations, such as, to amplification and/or the filtering of incoming signal.Pretreatment operation can adopt the form of any routine and depend on the essence of application and/or incoming signal.In an exemplary embodiment, pre-processing module 304 comprises amplifier (not shown in Fig. 3), is arranged to and the amplitude of incoming signal (being in particular peak amplitude) is set to reference levels.For this reason, if amplifier is variable gain amplifier, be then preferred.More specifically, by the amplitude basic setup of incoming signal be when comparing with reference value with in the corresponding level of the selected element (such as cutoff frequency) roll-offed on slope of the response of filter 306.This point is described in further detail below.
There is provided adjustable filter 306, for carrying out filtering (in this example after Signal Pretreatment) to incoming signal to produce the output signal through filtering.Filter 306 is high pass or low-pass filter typically, but can adopt other forms as an alternative, and such as band is logical or be with resistance.Filter 306 has at least one cutoff frequency (also referred to as corner frequency (corner frequency) or corner frequency (breakfrequency)), and it adjusts by the control signal received at input 307 place.Should or each cutoff frequency be limited to border between the passband of filter 306 or stopband.Typically, cutoff frequency be filter by the frequency of signal attenuation 3dB or more, although the level of decay can be limited to higher or lower level.In an exemplary embodiment, filter 306 is low-pass filter or high-pass filter, there is single cutoff frequency in this case.
Filter 306 can comprise analog filter or digital filter, fixed with application, and can adopt any suitable conventionally form.The form of the control signal received at input 307 place depends on the type of filter 307.Such as, for some analog filters, such as switched capacitor filter or some transducer-capacitive filters, control signal adopts the form of clock signal, the cutoff frequency of the frequency determination filter of described clock signal.For other filters, control signal can adopt different forms, and such as in digital filter, control signal can comprise the information for adjusting filter coefficient.
Device 300 comprises filter control module 308 further, and it measures at least one feature from the output signal through filtering of filter 306, and measured feature (or multiple) and reference value is compared.Depend on the result compared, control module 308 can adjust the cutoff frequency of filter 306.In a preferred embodiment, adjustment cutoff frequency, makes the basic frequency of incoming signal (i.e. the echo signal component (base frequency hereinafter referred to incoming signal) of incoming signal) in the frequency limit that the district of roll-offing of the response with filter 306 is corresponding.Typically, make the base frequency of incoming signal substantially at the chosen position place in district of roll-offing by adjustment cutoff frequency, such as the basic decay at filter 306 is in the frequency at acceptable level place, realizes this point.Routinely, the cutoff frequency of filter 306 can as the chosen position roll-offed in district, if particularly filter 306 introduces gain independent of frequency to signal, especially true, although can select the frequency higher or lower than cutoff frequency.
In a preferred embodiment, the feature through measuring of the output signal of filter 306 is or comprises the amplitude of output signal, the peak amplitude of output signal specifically.This point is illustrated, wherein for example, assuming that filter 306 is low-pass filters with reference to figure 4.When the undesirably component of signal of the incoming signal comprising noise is the frequency higher than base frequency, low-pass filter is used to be suitable as filter 306.
Fig. 4 is the figure of the typical frequency response of low-pass filter, and this frequency response has cutoff frequency Fc, thinks that the signal lower than cutoff frequency Fc will be passed through, and thinks the signal that will stop higher than cutoff frequency Fc.Response has district of roll-offing (slope) Ro, and along this district of roll-offing, signal increases along with its frequency and is attenuated gradually.Cutoff frequency Fc is located at and roll-offs on the Ro of slope.Expect to adjust filter response the maintains response substantially chosen position place of roll-offing on the Ro of slope with the frequency of the principal component by incoming signal.In this example, chosen position is substantially at cutoff frequency Fc place.Signal S1 represents the incoming signal with the basic base frequency at cutoff frequency Fc place.Because filtered device passes through by the signal at base frequency place, and filtered device stops by the higher frequency signal of such as noise effectively, so this is the serviceability expected.S2 represents the incoming signal of the base frequency F2 had lower than cutoff frequency Fc.The filtered device of signal S2 passes through, but is any less desirable component of signal of the frequency had between F2 and Fc too much.Thus expect to reduce Fc, preferably until it mates F2 substantially.Signal S3 represents the incoming signal of the base frequency F3 had higher than cutoff frequency Fc.The filtered device of signal S3 stops, so be necessary to increase Fc, preferably until it mates F3 substantially.
By the amplitude of measurement signal S1, S2, S3, filter controller 308 can determine that cutoff frequency Fc is the need of adjustment.This is because filter 306 is applied to the decay of signal level at Fc is known, so when Fc mates the base frequency of incoming signal, expectation range value about the output signal through filtering can be calculated from the amplitude of incoming signal (also considering any other gain that filter 306 and pre-processing module 304 are introduced).Therefore, if the amplitude of output signal measured is less than expectation value, then filter controller 308 can show that Fc is too low and should be enhanced.If the amplitude of output signal measured is greater than expectation value, then filter controller 308 can show that Fc is too high and should be lowered.If the value measured mates expectation value substantially, then Fc can be maintained its current setting.Thus, filter apparatus 300 can follow the tracks of the incoming signal of the base frequency with change.Assuming that the amplitude of the master of incoming signal or basic component is substantially invariable.Thus the output signal through filtering produced by device 300 is also typically substantially invariable amplitude (in tolerance limit, as will be described in further detail below).
In typical operation mode, initially cutoff frequency is set to relatively low value, and is increased by device 300, until the base frequency compatibility of itself and incoming signal.After this, the operation of device 300 impels amendment cutoff frequency, to follow the tracks of the change in the base frequency of incoming signal.
To be apparent that, but if the amplitude that corresponding relative operation mode is applicable to high-pass filter-measurement exceedes expectation value, then increase Fc; If the amplitude measured is less than expectation value, then reduce Fc.
Usually by be supplied in any suitable manner filter control module 308 or to filter control module 308 can with reference value (as illustrated in Figure 3) represent expectation value about the output signal through filtering.When device 300 comprises analogous circuit, can provide reference value with the form of electric signal (such as voltage level), described electric signal can provide from outside or inside source.In Digital embodiments, can remain in data memory (not shown) with reference to value.
In the embodiments of figure 3, filter controller 308 comprises filter and exports measurement module 310, it is configured to measure through the correlated characteristic (or multiple) of the output signal of filtering---be amplitude in this example, be preferably peak amplitude---and indicate to be supplied to and assess and control module 312.Assessment and control module 312 will export data that measurement module 310 receives and reference value compares from filter, and determine that cutoff frequency is the need of being increased, reducing or maintain its present level.Then assessment and control module 312 generate filter control signal in due course, and it is by the filter 306 that communicates via input 307.
Simulation embodiment in, assessment and control module 312 and filter output measurement module 310 can comprise any suitable analogous circuit, communicate each other and with filter 306 by means of electric signal.In Digital embodiments, assessment and control module 312, filter output measurement module 310 and filter 306 can be realized with software, hardware or its any combination suitably, in this case, a part or all communication and signaling can be performed with software, comprise filter control signal.
With reference now to Fig. 5, show the second embodiment of tracking filter apparatus 500.Device 500 is usually similar to filter apparatus 300, so used similar numeral to indicate similar portion, and will be apparent that for technical personnel, and be suitable for same description.
Filter apparatus 500 can be incorporated in the shock sensor interface of the type such as described above with reference to Fig. 2.Like this, incoming signal (the incoming signal A in Fig. 5) sends from the shock sensor rotated during use (not shown Fig. 5) or other equipment, and the base frequency of the electric signal produced by shock sensor or other equipment depends on the rotative speed of wheel.The noise component of incoming signal trends towards higher than base frequency in frequency, so device 500 comprises adjustable filter 506, it is configured to be used as low-pass filter, such as 2 pole lowpass filters.Device 500 also comprises variable gain amplifier 504(can provide other pre-process circuits, but for the sake of clarity not shown in Figure 5), for adjusting the level of incoming signal.Providing output signal metering circuit 510, for measuring in an amplitude for the output signal at O1 place, and generating the corresponding output signal being sent to assessment and control circuit 512.Alternatively, after filter 506, still can provide high-pass filter 514 before an O1, to remove any dc skew that may exist in the signal.
Output signal metering circuit 510 preferably includes peak detctor, and can comprise full-wave rectifying circuit, for carrying out rectification to the signal at O1 place.Metering circuit 510 such as, by means of peak detctor and any suitable voltage storage device, one or more cond, detects and remains on the peak amplitude value of the signal at O1 place.Metering circuit 510 is configured to produce output signal, is dc signal routinely, and it represents the peak value through measuring of the signal at O1 place.
Assessment and control circuit 512 comprise comparator 516, its be arranged to receive and comparison reference signal VREF(typically with the form of voltage signal) and the output signal of measurement mechanism 510.Comparator 516 depends on that the result compared produces and exports.In illustrated example, comparator 516 generates two output signals, i.e. UP signal and DOWN signal, if comparator 516 is determined to increase cutoff frequency Fc, claims UP signal, if comparator 516 is determined to reduce cutoff frequency Fc, claims DOWN signal.Assessment and control circuit 512 comprise clock signal generators 518 further, and it receives the output of comparator 516, and be configured to generate be supplied to control inputs 507 clock signal FCLK with the control inputs signal as adjustable filter 506.In this example, assuming that filter 506 is the types that can adjust by means of the change in the frequency of the clock signal provided at control inputs (such as switched capacitor filter) place.Clock signal generators 518 pairs of UP or DOWN signals respond the frequency increasing or reduce FCLK.
In a preferred embodiment, measurement mechanism (particularly when comprising peak detector circuit) is arranged to and operates with variable time constant.Advantageously, the output signal of self-clock signal generator 518 is supplied to measurement mechanism in the future, and the time constant of device 510 is changed according to the frequency of the signal detected.This has following effect: namely optimize, preferably minimize stabilization time, therefore shortens the time of tracking signal cost.It also contributes to reducing the overshoot or the undershoot that affect the filter 506 of signal output amplitude.
Technical personnel is apparent that, clock signal generators 518 can be realized by any suitable device.Such as, clock signal generators can comprise analog vco (VCO).Preferred clock generator is arranged to the substantially invariable rate of following of level and smooth change and the detection signal provided about the frequency of filter 506,506 '.
Preferably, when the output signal of Reference Signal and measurement compares, the degree of tolerance is allowed at the either side of reference signal, namely only when the signal measured is less than reference signal more than threshold quantity, or when being greater than reference signal more than threshold quantity, just think that the signal measured does not mate with reference signal.Can realize this point by using window type comparator as comparator 516, wherein comparator has the lower activation threshold (lower activation threshold) than reference signal Low threshold amount and the upper activation threshold (upper activation threshold) than reference signal high threshold amount.In this example, when the signal measured is less than lower activation threshold, UP signal is claimed; And when the signal measured is higher than upper activation threshold, claim DOWN signal (although if filter 506 is high-pass filters, can be contrary).The adjustment of this tolerance buffering cutoff frequency, and reduce internal circuit otherwise the impact that may have the operation of device 500.
Variable gain amplifier 504 has the gain input 520 that can be adjusted gain by it.The main purpose of amplifier 504 is that the amplitude of incoming signal is adjusted to following level: namely make based on by filter at cutoff frequency Fc(or other selected elements roll-offed on slope in the response of filter 506) the known decay of applying and consider may be applied to any other gain or the decay of incoming signal before the point measured it, the expectation range value of the output signal measured by metering circuit 510 is substantially identical with reference signal VREF.Result, base frequency and cutoff frequency Fc(or other selected elements roll-offed on slope in the response of filter 506 when incoming signal) when substantially mating, the output signal measured will have the amplitude substantially identical with reference signal VREF, in this case, will not adjust the value of Fc.But, when incoming signal base frequency not with cutoff frequency Fc(or other selected elements roll-offed on slope in the response of filter 506) substantially mate time, the output signal measured will have the amplitude more high or low than reference signal VREF, therefore will adjust the value of Fc as mentioned above.This layout has cutoff frequency Fc(or other selected elements roll-offed on slope in the response of filter 506) substantially remain on the effect at the base frequency place of incoming signal, and therefore device 500 can be called tracking incoming signal.
It should be noted that the position of roll-offing on slope being selected as the filter characteristic corresponding with the base frequency of incoming signal needs not to be cutoff frequency Fc.Such as, if filter 506 with any be associated component together with to increase to incoming signal suppose 12dB(or any other gain level) the gain independent of frequency, then at the-12dB(roll-offed on slope or other corresponding Reduction Levels) place's net gain of being applied to incoming signal is 0dB.Therefore ,-12dB(or other Reduction Levels) point can be the chosen position roll-offed in district.Expediently, select the slope of roll-offing of frequency response provides the point being essentially 0dB net gain, because this allows the amplitude of incoming signal to be adjusted to substantially to mate with the level of reference signal VREF.
In the example of hgure 5, the wheel monitoring device that device 500 is just using comprises two shock sensors, and each produces corresponding output signal.In order to process two shock sensor signals, with with for the identical mode of incoming signal A, provide corresponding variable gain amplifier 504 ', adjustable filter 506 ' and (if necessary) high-pass filter 514 ' to the second incoming signal, i.e. incoming signal B.But as shown in Figure 5, two filters 506,506 ' can share filter control circuit 510,512.Metering circuit 510 measures the amplitude of the output signal from two filter branch, and assessment and control circuit 512 produce common filter control signal for each filter 506,506 '.This layout has the effect of the phase relation maintained between filter 506,506 '.
In the illustrated embodiment in which, provide phase detectors 530, to determine the relative phase relation between the output signal of filtering from each shock sensor.Particularly, phase detectors 530 are arranged to determine in the output signal of filtering which lead over another, because this allows to carry out the determination (as at US 7,367, in 227 in greater detail) about the position of wheel on its vehicle.Therefore, the output signal of phase detectors 530 provides the instruction about wheel position.Before being provided to phase detectors 530, each passage passes such as sometimes referred to as the respective comparator 532,532 ' of the type of zero-crossing detector, and each is configured to generate the square wave corresponding through the output signal of filtering with corresponding reception.As obvious for technical personnel, phase detectors 530 can be realized by any suitable device.Understanding be the invention is not restricted to use phase detectors.
Fig. 6 A shows the specific embodiment of tracking filter apparatus 600 by example.Fig. 6 B shows the supplementary tracking filter apparatus 600 ' sharing common filter control circuit with filter apparatus 600.Device 600,600 ' is suitable for using in the circuit of Fig. 5 of the example as device 500,500 ' together.In figures 6 a and 6b, also corresponding shock sensor SS1, SS2 is shown, for providing corresponding incoming signal (although can alternatively use other sensors, be in particular motion sensor, accelerometer or accelerometer equipment), and the output of corresponding device 600,600 ' is shown for above being connected to about the respective comparator 632,632 ' described by Fig. 5.Filter apparatus 600,600 ' is usually similar to filter apparatus 500,500 ', so used similar numeral to indicate similar portion, and will be apparent that for technical personnel, and be suitable for same description.
Filter 606,606 ', as difference channel operation, receives the Differential Input from corresponding shock sensor SS1, SS2, and corresponding differential output signal is supplied to corresponding comparator 632,632 '.Pre-processing module 604,604 ' comprises differential amplifier, preferably has variable gain, and can comprise other pre-process circuits, such as, can be applicable to filter and/or the energy disperser of this application.
Adjustable filter 606,606 ' can adopt the form of any routine, such as switched capacitor tracking filter.In this example, the form of each employing switched capacitor low-pass filter of filter 606,606 ', preferably has 2 limit Barts fertile hereby (Butterworth) response.Select 2 pole filters, because it provides good decay and have not too precipitous slope of roll-offing, to control the signal amplitude on its slope.Control to have failure-free to filter position, as mentioned above, basis signal should be positioned on the slope of filter response.
Corresponding frequency double 609,611,609 ', 611 ' can be provided in input and output place of filter 606,606 '.Frequency double can be embodied as and there is the switched capacitor gain stage that gain is 2.These also provide filtering characteristics (typically being pole of order 1 frequency response), so in illustrated example, the filter response of input frequency double 609,609 ' to low-pass switched capacitor formula filter 606,606 ' has contribution.Export frequency double and also have pole of order 1 frequency response, but its limit is enough far away from the cutoff frequency Fc of filter 606,606 ', a little is not contributed to filter response to make it.
The cutoff frequency Fc of-3dB point of such as filter response adjusts by FCLK signal.Because filter 606,606 ' provides the gain (being the gain of 12dB in this example) independent of frequency, institute, so that control filter 606,606 ' and respond, provides basic neutralisation independent of the position (being namely-12dB the part on filter response slope in this example) of the corresponding decay of the impact of the gain of frequency the basic component of incoming signal to be positioned substantially at roll-offing of response in district.As a result, filter 606,606 ' does not have net impacts to the gain of system.
The basic component of signal is positioned on the slope of frequency response, downwards further than Fc on the slope particularly, wider tolerance is allowed to signal noise and change.
High-pass filter 614,614 ' is also difference channel.The object of high-pass filter 614,614 ' removes any dc skew, and accelerating and helping between deceleration period to take out the skew occurred on shock sensor SS1, SS2.For corresponding output comparator 632,632 ' and corresponding metering circuit 610,610 ', both provide feed-in to high-pass filter 614,614 '.For these both circuits, the dc skew that their input does not have existence is favourable.
High-pass filter 614,614 ' preferably has lowest possible cutoff frequency, to avoid the decay at low frequency place signal.High-pass filter 614,614 ' is eachly divided into 2 parts, a positive signal for differential signal, and another is for the negative signal of differential signal.Between the two halves being desirably in filter, there is good coupling.Owing to preferably there is low-down cutoff frequency, so may occur to leak and introduce skew.But two parts of regulation filter 614,614 ' are couplings, so do not cause differential offset, only there is common-mode offset.
Output comparator 632,632 ' is fully differential, and provides positive output and negative output, and be provided in the comparison of the voltage that its input two ends are seen, this generates the drift current generated with inside and forms the electric current compared.This equates and input voltage and the voltage excursion generated intentionally are compared, it occurs with the instruction of positive and negative.If input voltage exceedes internal offset voltage, plus or minus triggers by respectively.If it does not exceed activation threshold value, then both positive and negative output remains low.This provide square wave logic level signal, then it can be processed by phase detectors (not shown in Fig. 6 A and Fig. 6 B) further.
Metering circuit 610,610 ' comprises corresponding peak detctor.Peak detector circuit has the effect of biphase rectification to the signal that it receives.Peak detctor comprises two comparators 613A, 613B.Comparator 613A follows the tracks of the peak signal in the positive output of the differential signal received, and the negative output working as received differential signal becomes another comparator of timing 613B follows the tracks of this negative output.Exist for the single cond of signal maintenance and the switched capacitor resistor for biased (being 1.2V in this example) to reference signal.
Peak detector circuit is not difference.They are single-ended, and use the direct voltage output of the plus or minus part of the differential signal received, so be subject to the impact of common-mode offset.Buffer circuits 615 can be provided in the input of peak detctor.This mainly provides high input impedance to peak detctor.Can provide frequency multiplier circuit 617 in the output of energy disperser 615, it can be set to whether frequency multiplication.This arrangement provides may from the direct correction of any common-mode offset of high-pass filter 614.
To find out from Fig. 6 B, part metering circuit is reproduced, i.e. 613A ', 613B ', energy disperser 615 ' and frequency double 617 '.But, by combined for the output of the output and peak detctor 611 that are used for the peak detctor of this branch of circuit, as the connection A by occurring in Fig. 6 A and Fig. 6 B indicates, export to provide the combination peak detctor from the Liang Ge branch of circuit.
The output of peak detctor 610,610 ' is fed to comparator 616.Described by about Fig. 5, comparator has two outputs, i.e. UP and DOWN, and it is for carrying out roll-offing a little of the switched capacitor of mobile tracking filter 606,606 ' via the clock generator 618 generating FCLK signal.
By example, cond 616 can have the lower threshold value of 115mV and the upper threshold value of 185mV.Comparator 616 compares from the output of peak detctor and 150mV reference signal, and output as a result generates UP signal or DOWN signal.This allows the tolerance of +/-35mV on the either side of reference signal value.
As an alternative, can use and realize tracking filter apparatus of the present invention and process the signal sent from the equipment (particularly sensor) except shock sensor.Such as, tracking apparatus 300,500,600 can receive by the output signal of accelerometer, MEMS sensor or other motion sensors generation as incoming signal.As above about described by shock sensor, such sensor can use in pairs, so all two channel circuits as shwon in Figures 5 and 6 also can be used to process the output signal of other sensors (particularly motion sensor).
Pass through example, when using MEMS sensor as motion detector in wheel monitoring equipment, MEMS sensor suffers the problem similar with shock sensor, that is: because when attempting along with rotation of wheel detecting G power, also pick up the noise from road and signal, make to be difficult to G-signal to be separated with road noise.Can by certain frequency place by charge injection on condenser armature, and then use each sampling of capacitive character integrating circuit stored charge, from capacitive character MEMS sensor, extract G-signal.The change of electric capacity changes the accumulation voltage from integrator, can detect G-signal thus by amplifying this signal.Then amplifying signal can be delivered to and realize tracking filter apparatus of the present invention, with as it from the identical mode erasure signal of shock sensor.
MEMS sensor can have 2 or even 3 axles, but for this application, typically only uses 2 axles.When using MEMS sensor, the problem that may occur may have visibly different amplitude with the signal from Y-axis from the signal of X-axis, in this case, must be in harmonious proportion this difference in the amplifier gain of the different passages of tracking filter apparatus.
Advantageously, filter clock frequency signal FCLK can be used to calibrate tracking filter apparatus 300,500,600, make the gain of amplifier 504 (or the equivalence in signal pre-processing module (304,604) is amplified) adjustment filter 306,506,606 in the operational zone (as mentioned above) expected.In a preferred embodiment, between filter clock frequency and the base frequency of incoming signal, there is fixing relation.Typically, the frequency of filter clock frequency is the multiple (such as × 100) of base frequency.
When the gain of amplifier 304,504,604 is in aspiration level, the amplitude through the signal (such as some O1 place) in Figure 5 of filtering is mated substantially with reference value, and then filter clock frequency is the known multiple of fundamental signal frequency.Therefore, when correctly calibrating installation 300,500,600 time, base frequency can be determined according to filter clock frequency.Thus the wheel frequency (thus the speed of vehicle) of vehicle can be drawn from filter clock frequency.This information can be used to check whether tracking filter correctly works.Such as, another of the wheel velocity drawn from filter clock frequency and wheel velocity can be measured (it can be provided by any conventional means easily) to compare, and if two of wheel velocity are measured basic coupling, then can suppose that tracking filter apparatus correctly works.
Typically, by representing that the data of filter clock frequency are sent to other places of control unit 112 or vehicle, compare to perform.
When clock signal generators 518 comprises counting machine, the convenient manner obtained about the desired data of filter clock frequency is the value using the counting machine generating filter clock frequency.
Fig. 7 shows the alternative embodiment of the corresponding tracking filter apparatus about two shock sensors sharing common filter control circuit.Corresponding tracking filter apparatus is suitable for together in Figure 5 as the circuit of the example of device 500,500 '.In the figure 7, also illustrate that corresponding shock sensor is for providing corresponding incoming signal (although can use other sensors as an alternative, particularly motion sensor, accelerometer or accelerometer equipment), and the output of related device is shown for above being connected to about the respective comparator 732,732 ' that Fig. 5 describes.Filter apparatus is usually similar to filter apparatus 500,500 ', more specifically, is similar to device 600,600 ', so use similar numeral to indicate similar portion, and will be apparent that for technical personnel, and be suitable for same description.
The tracking filter apparatus of Fig. 7 comprises corresponding pre-processing module 704,704 ', comprises such as differential amplifier, preferably has variable gain, and can comprise other pre-process circuits, such as, can be applicable to filter and/or the energy disperser of this application.Adjustable filter 706,706 ' can adopt the form of any routine, such as switched capacitor tracking filter.In this example, the form of each employing low-pass filter of filter 706,706 '.Corresponding frequency double 709,711,709 ', 711 ' can be provided in input and output place of filter 706,706 '.
The tracking filter apparatus of Fig. 7 also comprises corresponding high-pass filter 714,714 ' and corresponding metering circuit 710,710 '.Metering circuit 710,710 ' comprises corresponding peak detctor, and each peak detctor comprises two comparators 713A, 713B and 713A ', 713B '.Corresponding buffer circuits 715,715 ' can be provided in the input of peak detctor.The output of peak detctor 710,710 ' is fed to comparator 716.Described by about Fig. 5, comparator has two outputs, i.e. UP and DOWN, and it is for carrying out roll-offing a little of moving switch condenser tracking filter 706,706 ' via the clock generator 718 generating FCLK signal.
In the embodiment of Fig. 7, high-pass filter 714,714 ' is adjustable filter, and can adopt the form of any routine, such as switched capacitor tracking filter.With what describe about filter 506,506 ' above being similar to, FCLK is supplied to high-pass filter 714,714 ', to adjust their filtering characteristics, is in particular their cut off.Corresponding low-pass filter 706,706 ' provides corresponding adjustable bands bandpass filter, i.e. tracking band-pass filter together with corresponding high-pass filter 714,714 ', and this adjustable bands bandpass filter has the passband that can adjust in response to the change in FCLK.
The tracking filter apparatus of Fig. 7 also comprises variable virtual impedance module 750.Module 750 is connected to the corresponding input of this or each tracking filter apparatus between shock sensor (or other input equipments) and adjustable filter 706,706 '.Module 750 provides variableimpedance in incoming signal path, such as variable resistance.Impedance or the resistance of presenting to corresponding incoming signal adjust by the control signal received by module 750.Expediently, control signal is provided by FCLK.Therefore, because impedance or resistance are controlled by FCLK, so it follows the tracks of the master of incoming signal or basic component.Help to create the substantially invariable amplitude input signals from shock sensor (or other input equipments), so this is favourable owing to following the tracks of input impedance.Which reduce and sometimes cause the result of the decay of the signal amplitude produced by shock sensor as the loaded impedance at shock sensor two ends and may at low frequency produced problem.Filter clock signal FCLK is fed to effective input impedance 750, to provide tracking input impedance, maintains substantially invariable incoming signal.
Variableimpedance module 750 can adopt any suitable form.Such as, it can comprise the network of transistor (typically being MOSFET), and it is arranged to as resistor.Module 750 receives FCLK effect for controlling to be applied to the control signal of the amount of the bias current of transistor.This can by any means easily (such as PWM(pulse duration modulation) current DAC (digital analog converter)) obtain.In a preferred embodiment, controlling to the bias current of transistor by means of PWM, FCLK, therefore control the impedance presented by module 750, is resistance in a preferred embodiment.Preferred module 750 comprises PWM current DAC.Actual effective resistance device can comprise current mirror, but, because the too low and voltage at equipment two ends very little (such as 0-790 μ V) of bias current, so MOSFET is in subthreshold value (sub threshold) district of operation, and in this mode, it serves as transistor.Therefore, in a preferred embodiment, module 750 can be described as effective resistance device, wherein use PWM current DAC to be biased the subthreshold value NMOS programmed by clock signal (FCLK), the frequency of described clock signal and the base frequency of just tracked incoming signal as one man change.The source of bias current can from internal oscillator, its when oscillator is trimmed to provide its correct frequency by automatic dressing.
In the embodiment of alternative, fully differential peak detctor can be used to carry out alternative above-described non-differential peak detctor.Which eliminate providing the needs leaking balanced circuit.
The invention is not restricted to embodiment described here, it can be modified when not deviating from scope of the present invention or change.

Claims (30)

1. a wheel supervisory system, comprise wheel monitoring equipment, described wheel monitoring equipment can be arranged on described wheel, and be configured to the first signal of the feature generating the described wheel of instruction, described wheel in use has variable rotational speed, described first signal has the basic frequency depending on described variable rotational speed, and wherein said wheel supervisory system comprises tracking filter apparatus further, and described tracking filter apparatus comprises:
Input, for receiving described first signal;
Adjustable filter, be arranged to the first signal receiving described first signal and produce through filtering, described adjustable filter has adjustable cutoff frequency; And
Filter controller, be arranged at least one feature measuring described the first signal through filtering, and at least one feature measured described and reference value are compared, described filter controller and described adjustable filter co-operating, if the amount different from described reference value at least one feature measured described exceedes threshold value, then adjust described cutoff frequency;
Wherein, described the first signal through filtering has the master signal component at described basic frequency place, and described master signal component has amplitude, and wherein, and described in described the first signal through filtering, at least one feature comprises the peak amplitude of described master signal component.
2. wheel supervisory system according to claim 1, wherein, described adjustable filter has the frequency response comprising district of roll-offing, in the described decay of the application of filter described in district with change of frequency of roll-offing, and wherein, described filter controller is arranged to the cutoff frequency adjusting described filter, make described basic frequency be in described in roll-off in district.
3. wheel supervisory system according to claim 2, wherein, described tracking filter apparatus is configured to described the first signal application through filtering independent of the gain of frequency, and wherein, described frequency controller is arranged to the cutoff frequency adjusting described filter, make described basic frequency be in described in the following position of roll-offing in district: in this position, the described decay of described filter application cancels the described gain independent of frequency at least in part on the impact of described the first signal through filtering.
4. wheel supervisory system according to claim 3, wherein, the decay that filter is applied at described cutoff frequency place described in the described attenuation ratio of described described location application of roll-offing in district of described filter is high.
5. the wheel supervisory system according to claim 3 or 4, wherein, described filter cancels the described gain independent of frequency to the entire effect of described the first signal through filtering substantially in the described decay of described described location application of roll-offing in district.
6. the wheel supervisory system according to claim 3 or 4, wherein, the described gain independent of frequency is applied by described adjustable filter at least partly.
7. the wheel supervisory system according to claim 3 or 4, wherein, described first signal and each in the first signal of filtering described have the master signal component at described basic frequency place, described master signal component has corresponding amplitude, and wherein, described tracking filter apparatus is included in the amplifier between described input and described adjustable filter further, described amplifier be arranged to when roll-off described in described basic frequency is in the selected position in district time, the amplitude of described first signal is adjusted to the level impelling the amplitude of described the first signal through filtering substantially to mate described reference value.
8. the wheel supervisory system according to claim 3 or 4, wherein, described adjustable filter comprises low-pass filter, and wherein, described filter controller and described adjustable filter co-operating, if exceed first threshold for the amount that reference value described at least one aspect ratio measured described is little, then increase described cutoff frequency, if and the amount that described at least one aspect ratio measured described, reference value is large exceedes Second Threshold, then reduce described cutoff frequency.
9. the wheel supervisory system according to claim 3 or 4, wherein, described adjustable filter comprises high-pass filter, and wherein, described filter controller and described adjustable filter co-operating, if exceed first threshold for the amount that reference value described at least one aspect ratio measured described is large, then increase described cutoff frequency, if and the amount that described at least one aspect ratio measured described, reference value is little exceedes Second Threshold, then reduce described cutoff frequency.
10. wheel supervisory system according to claim 1, wherein, described threshold value is zero.
11. wheel supervisory systems according to claim 3 or 4, wherein, described filter controller comprises peak detctor, and described peak detctor is for detecting the peak amplitude of described the first signal through filtering.
12. wheel supervisory systems according to claim 11, wherein, described peak detctor is configured to generate the direct current signal of the amplitude with the detected amplitude indicating described the first signal through filtering.
13. wheel supervisory systems according to claim 3 or 4, wherein, described filter controller comprises comparator, described comparator is arranged to and at least one feature measured described and described reference value is compared and produce at least one output signal, and at least one output signal described determines how to adjust described cutoff frequency.
14. wheel supervisory systems according to claim 3 or 4, wherein, described adjustable filter has control inputs, described control inputs is used for receive clock signal, wherein, described clock signal controls the cutoff frequency of described filter, and wherein, described filter controller comprises clock signal generators, described clock signal generators is for generating described clock signal, if the amount that described clock signal has at least one feature measured described different from described reference value exceedes described threshold value, the frequency adjusted by described clock signal generators.
15. wheel supervisory systems according to claim 3 or 4, wherein, described wheel monitoring equipment comprises the first motion sensor, and described first signal is generated by described first motion sensor.
16. wheel supervisory systems according to claim 3 or 4, wherein, described wheel monitoring equipment comprises tire pressure monitoring equipment.
17. wheel supervisory systems according to claim 15, wherein, described wheel monitoring equipment comprises the second motion sensor, described second motion sensor generates the secondary signal of the described feature of the described wheel of instruction, described secondary signal has the basic frequency depending on described variable rotational speed, wherein said wheel supervisory system comprises the second tracking filter apparatus further, and described second tracking filter apparatus comprises: input, for receiving described secondary signal, and adjustable filter, be arranged to the secondary signal receiving described secondary signal and produce through filtering, described adjustable filter has adjustable cutoff frequency, and wherein said filter controller is arranged at least one feature measuring the described secondary signal through filtering, and at least one feature measured described and described reference value are compared, the described adjustable filter co-operating of described filter controller and the second tracking filter apparatus, if the amount different from described reference value at least one feature measured described exceedes threshold value, then adjust described cutoff frequency.
18. wheel supervisory systems according to claim 17, comprise phase detectors further, described first and second each in the signal of filtering are provided to described phase detectors, and described phase detectors are arranged to determines the described first and second phase relations between the signal of filtering.
19. wheel supervisory systems according to claim 18, wherein, described wheel is installed on vehicle, and described system is arranged to and depends on that described phase relation carries out the determination about the position of described wheel on described vehicle.
20. wheel supervisory systems according to claim 1, wherein, described tracking filter apparatus is included in described wheel monitoring equipment.
21. wheel supervisory systems according to claim 17, wherein, described tracking filter apparatus and described second tracking apparatus are included in described wheel monitoring equipment.
22. wheel supervisory systems according to claim 17, wherein, described first motion sensor comprises shock sensor or accelerometer or MEMS (MEMS) sensor.
23. wheel supervisory systems according to claim 17, wherein, described second motion sensor comprises shock sensor or accelerometer or MEMS (MEMS) sensor.
24. wheel supervisory systems according to claim 17, comprise the adjustable impedance module be connected between described input and described adjustable filter further, described adjustable impedance module can be controlled by described filter controller, if the amount different from described reference value at least one feature measured described exceedes threshold value, then adjust the impedance of described adjustable impedance module.
25. wheel supervisory systems according to claim 24, wherein, described adjustable impedance module comprises the network of transistor, wherein, the described filter controller biased control inputs be arranged to described network provides the clock signal of pulse wave modulation, to control the bias current of described transistor.
26. 1 kinds of wheel monitoring equipments, described wheel monitoring equipment to be installed on wheel and to be configured to the first signal of the feature generating the described wheel of instruction, described wheel in use has variable rotational speed, described first signal has the basic frequency depending on described variable rotational speed, wherein said wheel monitoring equipment comprises tracking filter apparatus further, described tracking filter apparatus comprises: input, for receiving described first signal; Adjustable filter, be arranged to the first signal receiving described first signal and produce through filtering, described adjustable filter has adjustable cutoff frequency; And filter controller, be arranged at least one feature measuring described the first signal through filtering, and at least one feature measured described and reference value are compared, described filter controller and described adjustable filter co-operating, if the amount different from described reference value at least one feature measured described exceedes threshold value, then adjust described cutoff frequency;
Wherein, described the first signal through filtering has the master signal component at described basic frequency place, and described master signal component has amplitude, and wherein, and described in described the first signal through filtering, at least one feature comprises the peak amplitude of described master signal component.
27. 1 kinds of methods of following the tracks of the dominant frequency component of the first signal of wheel supervisory system, described wheel in use has variable rotational speed, described basic frequency depends on described variable rotational speed, wherein said wheel supervisory system comprises the adjustable filter with adjustable cutoff frequency further, and described method comprises:
Described adjustable filter is used to carry out filtering to produce the first signal through filtering to described first signal;
Measure at least one feature of described the first signal through filtering;
At least one feature measured described and reference value are compared; And
If the amount that at least one feature measured described is different from described reference value exceedes threshold value, then adjust described cutoff frequency;
Wherein, described the first signal through filtering has the master signal component at described basic frequency place, and described master signal component has amplitude, and wherein, and described in described the first signal through filtering, at least one feature comprises the peak amplitude of described master signal component.
28. methods according to claim 27, wherein, described adjustable filter has the control inputs for receive clock signal, wherein, described clock signal controls the cutoff frequency of described filter, and described method comprises: the measurement obtaining the speed of described wheel from described clock signal; The described measurement of described wheel velocity and the alternative measurement of described wheel velocity are compared; And if the described measurement of described wheel velocity and described alternative measure basic coupling, then determine that described adjustable filter correctly operates.
29. 1 kinds of tracking filter apparatuses, comprising:
Input, for receiving the first signal, the vicissitudinous basic frequency of described first signal tool;
Adjustable filter, be arranged to the first signal receiving described first signal and produce through filtering, described adjustable filter has adjustable cutoff frequency; And
Filter controller, be arranged at least one feature measuring described the first signal through filtering, and at least one feature measured described and reference value are compared, described filter controller and described adjustable filter co-operating, if the amount different from described reference value at least one feature measured described exceedes threshold value, then adjust described cutoff frequency;
Wherein, described the first signal through filtering has the master signal component at described basic frequency place, and described master signal component has amplitude, and wherein, and described in described the first signal through filtering, at least one feature comprises the peak amplitude of described master signal component.
The method of the dominant frequency component of the first signal in 30. 1 kinds of track channels, described system comprises the adjustable filter with adjustable cutoff frequency, and described method comprises:
Described adjustable filter is used to carry out filtering to produce the first signal through filtering to described first signal;
Measure at least one feature of described the first signal through filtering;
At least one feature measured described and reference value are compared; And
If the amount that at least one feature measured described is different from described reference value exceedes threshold value, then adjust described cutoff frequency;
Wherein, described the first signal through filtering has the master signal component at described basic frequency place, and described master signal component has amplitude, and wherein, and described in described the first signal through filtering, at least one feature comprises the peak amplitude of described master signal component.
CN201080052199.2A 2009-09-18 2010-09-17 Tracking filter apparatus for wheel monitoring systems Active CN102686418B (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB0916369.2 2009-09-18
GBGB0916369.2A GB0916369D0 (en) 2009-09-18 2009-09-18 Tracking filter apparatus for wheel monitoring systems
PCT/EP2010/005712 WO2011032713A1 (en) 2009-09-18 2010-09-17 Tracking filter apparatus for wheel monitoring systems

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CA2774454A1 (en) 2011-03-24

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